The present invention relates to a semiconductor device for performing an inverter control provided with AD converters, and a control method using the same.
FIG. 8A and FIG. 8B are diagrams illustrating a general structure of a conventional motor control device. The structure of FIG. 8A employs an inverter control microcomputer 60 for an inverter control of a motor 71. As illustrated in FIG. 8B, the inverter control microcomputer 60 includes an inverter control signal generation circuit 65 and an AD converter 66, in addition to a CPU 61, a ROM 62, a RAM 63, an I/O port 64, etc.
In the prior art, in order to meet the demand for conserving energy, an analog value is used as a position detection signal, and the input analog value is converted into a digital value by using an AD converter provided in a microcomputer so as to perform a control using the digital value. Specifically, the inverter control microcomputer 60 converts an input position detection signal into a digital value using the AD converter 66, and calculates the position of the rotor of the motor using the CPU 61. An inverter control signal is generated by the inverter control signal generation circuit 65 based on the position data so as to control the motor.
When driving a 3-phase motor, two analog signals are preferably used as position detection signals. However, with the structure of FIG. 8B, having only one AD converter, two analog signals need to be AD-converted one by one. Since the two signals cannot be AD-converted simultaneously, there will be a certain shift in conversion timing between the two signals. However, the motor 71 is always rotating, whereby the shift in detection timing between the two signals may cause a problem in terms of the control precision.
In order to solve such a problem, a microcomputer provided with two AD converters 67a and 67b, as illustrated in FIG. 9, has been commercialized. The use of such a microcomputer allows for simultaneous AD conversion of two position detection signals, thereby enabling a high-precision control.
Regarding an inverter control of a motor, the revision of Japanese Law concerning the Rational Use of Energy and the introduction of Limits for Harmonic Current Emissions have necessitated a control of the power to be supplied to the motor in addition to the need to efficiently control the motor.
The power supply can be controlled, for example, by separately providing an analog circuit, or using a microcomputer or a DSP, for controlling the power supply, as illustrated in FIG. 10. However, with such a method, the size of the system as a whole increases, thereby increasing the production cost.
An object of the present invention is to provide a semiconductor device for an inverter control of a motor capable of appropriately performing a power supply control in addition to a motor control.
Specifically, the present invention provides a semiconductor device for performing an inverter control of a motor, including: a plurality of AD converters each converting an input analog signal into a digital signal; and a control circuit for processing the digital signals output from the plurality of AD converters so as to generate a control signal, wherein at least one of the plurality of AD converters is not used for controlling the motor but used for controlling a power supply of the motor while receiving an analog signal representing a state of the power supply.
With the semiconductor device, at least one of the plurality of AD converters is not used for controlling the motor but used for controlling the power supply of the motor. Therefore, an AD conversion for a power supply control can be performed simultaneously with that for a motor control. Thus, it is possible to prevent an AD conversion from being delayed due to a contention between the timing of an AD conversion for a motor control and that for a power supply control, whereby it is possible to set appropriate carrier frequencies for a motor control and for a power supply control. Therefore, it is possible to appropriately perform a motor control and a power supply control together without adding any new hardware for a power supply control.
In the semiconductor device for performing an inverter control, it is preferred that the plurality of AD converters and the control circuit are provided in a 1-chip microcomputer.
The present invention also provides a method for performing an inverter control of a motor, including: a first step of converting an analog signal representing a state of the motor into a digital signal and performing an inverter control of the motor by using the conversion result; and a second step of converting an analog signal representing a state of a power supply of the motor into a digital signal and controlling the power supply by using the conversion result, wherein the first step and the second step are performed by using separate AD converters provided in a single semiconductor device.
The present invention also provides a method for performing an inverter control of motors, including: a first step of converting an analog signal representing a state of a first motor into a digital signal and performing an inverter control of the first motor by using the conversion result; and a second step of converting an analog signal representing a state of a second motor into a digital signal and performing an inverter control of the second motor by using the conversion result, wherein the first step and the second step are performed by using separate AD converters provided in a single semiconductor device.
The present invention also provides a semiconductor device for performing an inverter control of a motor, including: a number of AD converters each converting an input analog signal into a digital signal; and a control circuit for processing the digital signals output from the AD converters so as to generate a control signal, wherein the number of AD converters is three or more.
In the semiconductor device for performing an inverter control of a motor, it is preferred that the AD converters and the control circuit are provided in a 1-chip microcomputer.